2 private and one public address

I need to resolve following problem:
a) my customer has computer connected to internet, but he has private ip address (rs3 installed)
b) i have computer with private address too (rv3 installed)
c) i need connect from my pc (private ip) to customer pc (private ip)(i'm thinking this is not possible) but ...
d) i have my own remote server with public ip address, is any way to connect from my pc to server and from server to customer pc? If not, is any other way, how to resolve this problem?